This invention relates to a dot matrix printer and, more particularly to improvement of its carriage assembly including a printer hammer bank which comprises a plurality of printer hammers aligned in the direction perpendicular to feeding direction of a paper set on the platen of the printer to be printed.
The dot matrix printer is able to perform high speed operation to print various kinds of characters. It has become popular to use the type of printer as an output means for systems such as a computer or the like.
As is known well, the printing speed of such a printer is basically determined by two factors. One is a period required for one reciprocation of the printer hammer bank and the other is a period required for repetitive printing motion of printer hammers which are aligned in parallel with each other on the printer head. To realize high speed operation, therefore, shortening of both of these periods is required. It should be noted, however, that the printer head contains a lot of components itself, thus resulting in a considerably large inertia when the head is moving. Accordingly, the faster the printer is operated, more undesirable vibration is caused and noise also increases.
To solve the problem of high speed operation of the printer, an improved printer was proposed in the copending application Ser. No. 55,476 entitled "A Dot Matrix Type Printer" and filed on July 6, 1979, now U.S. Pat. No. 4,306,497 issued on Dec. 22, 1981. In the proposed printer, a carriage assembly includes a printer hammer bank which comprises a plurality of printer hammers aligned immediately before a sheet of paper set on a platen to be printed and in a direction perpendicular to a feeding direction of the paper, a balancing means, a first resilient member connecting the balancing means with the printer hammer bank, and a second resilient member connecting the balancing means with a printer frame. The printer hammer bank is driven to reciprocate in the direction perpendicular to the paper feeding direction by a driving source fixed to the printer frame. The balancing means has a mass matching with that of the printer hammer bank to suppress generation of vibration and noise due to the reciprocation of the printer hammer bank during the operation of the printer. Therefore, it is quite difficult to design a small-sized and light-weight printer.